1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the same and, more particularly, to a semiconductor device having a nonvolatile memory (FeRAM: Ferroelectric Random Access Memory) in which ferroelectric material is employed as the dielectric film of the capacitor and a method of manufacturing the same.
2. Description of the Prior Art
In the FeRAM, the cell area will be more reduced in response to the demand for the higher integration in the future. If the cell area is reduced in such a way, the interval between neighboring capacitors is also shortened and the wiring interval is also narrowed accordingly. It is general that the spaces between the capacitors and the spaces between the wirings are buried with the insulating film. In this case, if the higher integration makes progress as above, the insulating film having the good filling property not to form the cavity (also called as the blowhole or the void) between the capacitors must be employed as such insulating film.
As the insulating film having the good filling property, the film that is formed by the high density plasma CVD (HDPCVD) method is known in the prior art.
The insulating film that is formed by the HDPCVD method can be shown in FIG. 1 of Patent Application Publication (KOKAI) 2001-210798, for example. In this Publication, it is disclosed in the paragraph number 0042 that the HDP oxide can be used as the insulating film 134 for covering the capacitor in FIG. 1.
Similarly, in Patent Application Publication (KOKAI) 2001-230382, it is disclosed in the paragraph number 0084 that the HDP oxide can be used as the insulating film 408 for covering the capacitor in FIG. 4a.
Meanwhile, SiH4 is used in general as the film forming gas in the HDPCVD method. This SiH4 is decomposed during the film formation to generate the hydrogen. Thus, there is given the chance that the ferroelectric film of the capacitor is exposed to the hydrogen.
However, if the ferroelectric film is exposed to the reducing material such as the hydrogen or the like, the deterioration of the ferroelectric characteristic is brought about. Therefore, any measure for preventing such deterioration is needed.
In the usual plasma CVD method that is not the HDPCVD method, as the method of isolating the ferroelectric film from the hydrogen, the structure for covering the capacitor with the insulating film made of the metal oxide, e.g., the alumina (Al2O3) film, is known. Such structure is disclosed in Patent Application Hei 11-215600, Patent Application Publication (KOKAI) 2001-44375, Patent Application Publication (KOKAI) Hei 6-29098, and Japanese Patent No. 3056973.
However, it is made apparent by the inventors of the present invention that, in the HDPCVD method, this alumina film is not enough to block the hydrogen and thus the deterioration of the ferroelectric film is caused by the hydrogen.